"use strict";

var CHAR_TILDE = 126;
var CODE_FNC1 = 102;

var SET_STARTA = 103;
var SET_STARTB = 104;
var SET_STARTC = 105;
var SET_SHIFT = 98;
var SET_CODEA = 101;
var SET_CODEB = 100;
var SET_STOP = 106;

var REPLACE_CODES = {
    CHAR_TILDE: CODE_FNC1 //~ corresponds to FNC1 in GS1-128 standard
};

var CODESET = {
    ANY: 1,
    AB: 2,
    A: 3,
    B: 4,
    C: 5
};

function getBytes(str) {
    var bytes = [];
    for (var i = 0; i < str.length; i++) {
        bytes.push(str.charCodeAt(i));
    }
    return bytes;
}

exports.code128 = function (ctx, text, width, height) {

    width = parseInt(width);

    height = parseInt(height);

    var codes = stringToCode128(text);

    var g = new Graphics(ctx, width, height);

    var barWeight = g.area.width / ((codes.length - 3) * 11 + 35);

    var x = g.area.left;
    var y = g.area.top;
    for (var i = 0; i < codes.length; i++) {
        var c = codes[i];
        //two bars at a time: 1 black and 1 white
        for (var bar = 0; bar < 8; bar += 2) {
            var barW = PATTERNS[c][bar] * barWeight;
            // var barH = height - y - this.border;
            var barH = height - y;
            var spcW = PATTERNS[c][bar + 1] * barWeight;

            //no need to draw if 0 width
            if (barW > 0) {
                g.fillFgRect(x, y, barW, barH);
            }

            x += barW + spcW;
        }
    }
    ctx.draw(true);
};

function stringToCode128(text) {

    var barc = {
        currcs: CODESET.C
    };

    var bytes = getBytes(text);
    //decide starting codeset
    var index = bytes[0] == CHAR_TILDE ? 1 : 0;

    var csa1 = bytes.length > 0 ? codeSetAllowedFor(bytes[index++]) : CODESET.AB;
    var csa2 = bytes.length > 0 ? codeSetAllowedFor(bytes[index++]) : CODESET.AB;
    barc.currcs = getBestStartSet(csa1, csa2);
    barc.currcs = perhapsCodeC(bytes, barc.currcs);

    //if no codeset changes this will end up with bytes.length+3
    //start, checksum and stop
    var codes = new Array();

    switch (barc.currcs) {
        case CODESET.A:
            codes.push(SET_STARTA);
            break;
        case CODESET.B:
            codes.push(SET_STARTB);
            break;
        default:
            codes.push(SET_STARTC);
            break;
    }

    for (var i = 0; i < bytes.length; i++) {
        var b1 = bytes[i]; //get the first of a pair
        //should we translate/replace
        if (b1 in REPLACE_CODES) {
            codes.push(REPLACE_CODES[b1]);
            i++; //jump to next
            b1 = bytes[i];
        }

        //get the next in the pair if possible
        var b2 = bytes.length > i + 1 ? bytes[i + 1] : -1;

        codes = codes.concat(codesForChar(b1, b2, barc.currcs));
        //code C takes 2 chars each time
        if (barc.currcs == CODESET.C) i++;
    }

    //calculate checksum according to Code 128 standards
    var checksum = codes[0];
    for (var weight = 1; weight < codes.length; weight++) {
        checksum += weight * codes[weight];
    }
    codes.push(checksum % 103);

    codes.push(SET_STOP);

    //encoding should now be complete
    return codes;

    function getBestStartSet(csa1, csa2) {
        //tries to figure out the best codeset
        //to start with to get the most compact code
        var vote = 0;
        vote += csa1 == CODESET.A ? 1 : 0;
        vote += csa1 == CODESET.B ? -1 : 0;
        vote += csa2 == CODESET.A ? 1 : 0;
        vote += csa2 == CODESET.B ? -1 : 0;
        //tie goes to B due to my own predudices
        return vote > 0 ? CODESET.A : CODESET.B;
    }

    function perhapsCodeC(bytes, codeset) {
        for (var i = 0; i < bytes.length; i++) {
            var b = bytes[i];
            if ((b < 48 || b > 57) && b != CHAR_TILDE) return codeset;
        }
        return CODESET.C;
    }

    //chr1 is current byte
    //chr2 is the next byte to process. looks ahead.
    function codesForChar(chr1, chr2, currcs) {
        var result = [];
        var shifter = -1;

        if (charCompatible(chr1, currcs)) {
            if (currcs == CODESET.C) {
                if (chr2 == -1) {
                    shifter = SET_CODEB;
                    currcs = CODESET.B;
                } else if (chr2 != -1 && !charCompatible(chr2, currcs)) {
                    //need to check ahead as well
                    if (charCompatible(chr2, CODESET.A)) {
                        shifter = SET_CODEA;
                        currcs = CODESET.A;
                    } else {
                        shifter = SET_CODEB;
                        currcs = CODESET.B;
                    }
                }
            }
        } else {
            //if there is a next char AND that next char is also not compatible
            if (chr2 != -1 && !charCompatible(chr2, currcs)) {
                //need to switch code sets
                switch (currcs) {
                    case CODESET.A:
                        shifter = SET_CODEB;
                        currcs = CODESET.B;
                        break;
                    case CODESET.B:
                        shifter = SET_CODEA;
                        currcs = CODESET.A;
                        break;
                }
            } else {
                //no need to shift code sets, a temporary SHIFT will suffice
                shifter = SET_SHIFT;
            }
        }

        //ok some type of shift is nessecary
        if (shifter != -1) {
            result.push(shifter);
            result.push(codeValue(chr2));
        } else {
            if (currcs == CODESET.C) {
                //include next as well
                result.push(codeValue(chr1, chr2));
            } else {
                result.push(codeValue(chr1));
            }
        }
        barc.currcs = currcs;

        return result;
    }
}

//reduce the ascii code to fit into the Code128 char table
function codeValue(chr1, chr2) {
    if (typeof chr2 == "undefined") {
        return chr1 >= 32 ? chr1 - 32 : chr1 + 64;
    } else {
        return parseInt(String.fromCharCode(chr1) + String.fromCharCode(chr2));
    }
}

function charCompatible(chr, codeset) {
    var csa = codeSetAllowedFor(chr);
    if (csa == CODESET.ANY) return true;
    //if we need to change from current
    if (csa == CODESET.AB) return true;
    if (csa == CODESET.A && codeset == CODESET.A) return true;
    if (csa == CODESET.B && codeset == CODESET.B) return true;
    return false;
}

function codeSetAllowedFor(chr) {
    if (chr >= 48 && chr <= 57) {
        //0-9
        return CODESET.ANY;
    } else if (chr >= 32 && chr <= 95) {
        //0-9 A-Z
        return CODESET.AB;
    } else {
        //if non printable
        return chr < 32 ? CODESET.A : CODESET.B;
    }
}

var Graphics = function Graphics(ctx, width, height) {

    this.width = width;
    this.height = height;
    this.quiet = Math.round(this.width / 40);

    this.border_size = 0;
    this.padding_width = 0;

    this.area = {
        width: width - this.padding_width * 2 - this.quiet * 2,
        height: height - this.border_size * 2,
        top: this.border_size - 4,
        left: this.padding_width + this.quiet
    };

    this.ctx = ctx;
    this.fg = "#000000";
    this.bg = "#ffffff";

    // fill background
    this.fillBgRect(0, 0, width, height);

    // fill center to create border
    this.fillBgRect(0, this.border_size, width, height - this.border_size * 2);
};

//use native color
Graphics.prototype._fillRect = function (x, y, width, height, color) {
    this.ctx.setFillStyle(color);
    this.ctx.fillRect(x, y, width, height);
};

Graphics.prototype.fillFgRect = function (x, y, width, height) {
    this._fillRect(x, y, width, height, this.fg);
};

Graphics.prototype.fillBgRect = function (x, y, width, height) {
    this._fillRect(x, y, width, height, this.bg);
};

var PATTERNS = [[2, 1, 2, 2, 2, 2, 0, 0], // 0
[2, 2, 2, 1, 2, 2, 0, 0], // 1
[2, 2, 2, 2, 2, 1, 0, 0], // 2
[1, 2, 1, 2, 2, 3, 0, 0], // 3
[1, 2, 1, 3, 2, 2, 0, 0], // 4
[1, 3, 1, 2, 2, 2, 0, 0], // 5
[1, 2, 2, 2, 1, 3, 0, 0], // 6
[1, 2, 2, 3, 1, 2, 0, 0], // 7
[1, 3, 2, 2, 1, 2, 0, 0], // 8
[2, 2, 1, 2, 1, 3, 0, 0], // 9
[2, 2, 1, 3, 1, 2, 0, 0], // 10
[2, 3, 1, 2, 1, 2, 0, 0], // 11
[1, 1, 2, 2, 3, 2, 0, 0], // 12
[1, 2, 2, 1, 3, 2, 0, 0], // 13
[1, 2, 2, 2, 3, 1, 0, 0], // 14
[1, 1, 3, 2, 2, 2, 0, 0], // 15
[1, 2, 3, 1, 2, 2, 0, 0], // 16
[1, 2, 3, 2, 2, 1, 0, 0], // 17
[2, 2, 3, 2, 1, 1, 0, 0], // 18
[2, 2, 1, 1, 3, 2, 0, 0], // 19
[2, 2, 1, 2, 3, 1, 0, 0], // 20
[2, 1, 3, 2, 1, 2, 0, 0], // 21
[2, 2, 3, 1, 1, 2, 0, 0], // 22
[3, 1, 2, 1, 3, 1, 0, 0], // 23
[3, 1, 1, 2, 2, 2, 0, 0], // 24
[3, 2, 1, 1, 2, 2, 0, 0], // 25
[3, 2, 1, 2, 2, 1, 0, 0], // 26
[3, 1, 2, 2, 1, 2, 0, 0], // 27
[3, 2, 2, 1, 1, 2, 0, 0], // 28
[3, 2, 2, 2, 1, 1, 0, 0], // 29
[2, 1, 2, 1, 2, 3, 0, 0], // 30
[2, 1, 2, 3, 2, 1, 0, 0], // 31
[2, 3, 2, 1, 2, 1, 0, 0], // 32
[1, 1, 1, 3, 2, 3, 0, 0], // 33
[1, 3, 1, 1, 2, 3, 0, 0], // 34
[1, 3, 1, 3, 2, 1, 0, 0], // 35
[1, 1, 2, 3, 1, 3, 0, 0], // 36
[1, 3, 2, 1, 1, 3, 0, 0], // 37
[1, 3, 2, 3, 1, 1, 0, 0], // 38
[2, 1, 1, 3, 1, 3, 0, 0], // 39
[2, 3, 1, 1, 1, 3, 0, 0], // 40
[2, 3, 1, 3, 1, 1, 0, 0], // 41
[1, 1, 2, 1, 3, 3, 0, 0], // 42
[1, 1, 2, 3, 3, 1, 0, 0], // 43
[1, 3, 2, 1, 3, 1, 0, 0], // 44
[1, 1, 3, 1, 2, 3, 0, 0], // 45
[1, 1, 3, 3, 2, 1, 0, 0], // 46
[1, 3, 3, 1, 2, 1, 0, 0], // 47
[3, 1, 3, 1, 2, 1, 0, 0], // 48
[2, 1, 1, 3, 3, 1, 0, 0], // 49
[2, 3, 1, 1, 3, 1, 0, 0], // 50
[2, 1, 3, 1, 1, 3, 0, 0], // 51
[2, 1, 3, 3, 1, 1, 0, 0], // 52
[2, 1, 3, 1, 3, 1, 0, 0], // 53
[3, 1, 1, 1, 2, 3, 0, 0], // 54
[3, 1, 1, 3, 2, 1, 0, 0], // 55
[3, 3, 1, 1, 2, 1, 0, 0], // 56
[3, 1, 2, 1, 1, 3, 0, 0], // 57
[3, 1, 2, 3, 1, 1, 0, 0], // 58
[3, 3, 2, 1, 1, 1, 0, 0], // 59
[3, 1, 4, 1, 1, 1, 0, 0], // 60
[2, 2, 1, 4, 1, 1, 0, 0], // 61
[4, 3, 1, 1, 1, 1, 0, 0], // 62
[1, 1, 1, 2, 2, 4, 0, 0], // 63
[1, 1, 1, 4, 2, 2, 0, 0], // 64
[1, 2, 1, 1, 2, 4, 0, 0], // 65
[1, 2, 1, 4, 2, 1, 0, 0], // 66
[1, 4, 1, 1, 2, 2, 0, 0], // 67
[1, 4, 1, 2, 2, 1, 0, 0], // 68
[1, 1, 2, 2, 1, 4, 0, 0], // 69
[1, 1, 2, 4, 1, 2, 0, 0], // 70
[1, 2, 2, 1, 1, 4, 0, 0], // 71
[1, 2, 2, 4, 1, 1, 0, 0], // 72
[1, 4, 2, 1, 1, 2, 0, 0], // 73
[1, 4, 2, 2, 1, 1, 0, 0], // 74
[2, 4, 1, 2, 1, 1, 0, 0], // 75
[2, 2, 1, 1, 1, 4, 0, 0], // 76
[4, 1, 3, 1, 1, 1, 0, 0], // 77
[2, 4, 1, 1, 1, 2, 0, 0], // 78
[1, 3, 4, 1, 1, 1, 0, 0], // 79
[1, 1, 1, 2, 4, 2, 0, 0], // 80
[1, 2, 1, 1, 4, 2, 0, 0], // 81
[1, 2, 1, 2, 4, 1, 0, 0], // 82
[1, 1, 4, 2, 1, 2, 0, 0], // 83
[1, 2, 4, 1, 1, 2, 0, 0], // 84
[1, 2, 4, 2, 1, 1, 0, 0], // 85
[4, 1, 1, 2, 1, 2, 0, 0], // 86
[4, 2, 1, 1, 1, 2, 0, 0], // 87
[4, 2, 1, 2, 1, 1, 0, 0], // 88
[2, 1, 2, 1, 4, 1, 0, 0], // 89
[2, 1, 4, 1, 2, 1, 0, 0], // 90
[4, 1, 2, 1, 2, 1, 0, 0], // 91
[1, 1, 1, 1, 4, 3, 0, 0], // 92
[1, 1, 1, 3, 4, 1, 0, 0], // 93
[1, 3, 1, 1, 4, 1, 0, 0], // 94
[1, 1, 4, 1, 1, 3, 0, 0], // 95
[1, 1, 4, 3, 1, 1, 0, 0], // 96
[4, 1, 1, 1, 1, 3, 0, 0], // 97
[4, 1, 1, 3, 1, 1, 0, 0], // 98
[1, 1, 3, 1, 4, 1, 0, 0], // 99
[1, 1, 4, 1, 3, 1, 0, 0], // 100
[3, 1, 1, 1, 4, 1, 0, 0], // 101
[4, 1, 1, 1, 3, 1, 0, 0], // 102
[2, 1, 1, 4, 1, 2, 0, 0], // 103
[2, 1, 1, 2, 1, 4, 0, 0], // 104
[2, 1, 1, 2, 3, 2, 0, 0], // 105
[2, 3, 3, 1, 1, 1, 2, 0] // 106
];